Axial piston machine

ABSTRACT

An axial piston machine may include a a housing having vapor, cylinder chamber and wobble-plate chambers. The machine may have cylinders arranged annularly around a shaft in the cylinder chamber and having pistons arranged therein in a translationally movable manner, a valve disk connected to the shaft in a rotationally fixed manner and arranged in the vapor chamber, and a wobble plate connected to one of the pistons via a cup and ball bearing and to the shaft in a rotationally fixed manner, the wobble plate being arranged in the wobble-plate chamber. The housing may have steam-chamber, cylinder, and wobble-plate housing parts connected to one another. A cylinder sleeve having a radially protruding collar may be provided in at least one cylinder, wherein the cylinder sleeve may be retained via the collar in a cut-out in the cylinder housing part, which may adjoin a parting plane between the vapor-chamber and cylinder housing parts. The vapor chamber may be closed off by a first cover, which may be connected to the vapor-chamber housing part and which may be designed as a shaped sheet-metal part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Patent Application No. PCT/EP2016/059693, filed on Apr. 29, 2016, and German Patent Application No. DE 10 2015 207 909.0, filed on Apr. 29, 2015, the contents of both of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an axial piston machine comprising a housing, in which a vapor chamber, a cylinder chamber and a wobble-plate chamber are provided. Moreover, the invention relates to a heat recovery system in a motor vehicle comprising at least one such axial piston machine.

BACKGROUND

A plurality of generic axial piston machines comprising a housing is known from the prior art, in which a vapor chamber, a cylinder chamber as well as a wobble-plate chamber are provided. A rotor comprising a shaft as well as the wobble plate arranged thereon in a rotationally fixed manner and a valve disk, which is also connected to the shaft in a rotationally fixed manner, are also arranged in the housing. The wobble plate, which is in each case coupled to one of the pistons via a cup and ball bearing and which is coupled to the shaft in a rotationally fixed manner, is arranged in the wobble-plate chamber itself. Such axial piston machines are in particular used in so-called heat recovery systems in motor vehicles, in which they convert thermal energy into mechanical energy.

However, the comparatively extensive and expensive production is a disadvantage of the piston machine known from the prior art.

The invention at hand thus deals with the problem of specifying an improved or at least an alternative embodiment for an axial piston machine of the generic type, which is characterized in particular by a structurally simple and cost-efficient production.

According to the invention, this problem is solved by means of the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

SUMMARY

The present invention is based on the general idea of now embodying a housing of an axial piston machine, which is comparatively extensive and thus expensive to produce until now, in several parts and to thus disentangle the extremely complex production process. In a known manner, the axial piston machine according to the invention thereby has a housing, in which a vapor chamber, a cylinder chamber and a wobble-plate chamber are arranged. Cylinders, in which pistons are arranged in a translationally movable manner, are provided annularly around a shaft in the cylinder chamber. A valve disk, which is connected to the shaft in a rotationally fixed manner and which connects the vapor chamber so as to communicate with one of the cylinders or separates it therefrom, depending on the rotational position of the vapor chamber, is arranged in the vapor chamber itself. A wobble plate, which is connected to one of the pistons via a cup and ball bearing each and which is coupled to the shaft in a rotationally fixed manner, is arranged in the wobble-plate chamber. According to the invention, the housing now has a steam-chamber housing part, a cylinder housing part and a wobble-plate housing part, which are connected to one another. Moreover, a cylinder sleeve comprising a radially protruding collar is provided in at least one cylinder, wherein the cylinder sleeve is retained by means of its collar in a cut-out in the cylinder housing part, which adjoins a parting plane between the vapor-chamber housing part and the cylinder housing part. The vapor chamber itself is closed by means of a first cover, which is connected to the vapor-chamber housing part and which is designed as a shaped sheet-metal part. By means of the at least three housing parts, which, in the mounted state, form the housing of the axial piston machine, the individual housing parts can be produced in a simpler and more lightweight manner, wherein an insertion of the cylinder sleeve into the cylinder is additionally possible from the vapor-chamber housing part. By means of the cylinder sleeve, which is inserted into the respective cylinders, the load capacity of the axial piston machine according to the invention can be increased significantly and the production effort thereof can be reduced significantly, because an individual post-processing of the cylinder tracks, which can only be accomplished with difficulties in the case of the housings, which have been provided to date, can now be forgone completely. Via the first cover, by means of which the vapor chamber can be closed off, a cover, which has been formed integrally with the vapor-chamber housing part until now, can also be forgone, whereby the production can be simplified, in turn. By designing the first cover as shaped sheet-metal part, this cover can moreover not only be designed in a more cost-efficient manner, but also thinner, because such a shaped sheet-metal part is able to reliably bear higher forces, as compared to a cover, for example, which is designed as a cast part. By segmenting the housing into the individual housing parts, in particular a comparatively simple and, associated therewith, a cost-efficient production of the individual housing parts and, via the latter, of the entire housing, is thus also possible.

In the case of an advantageous further development of the solution according to the invention, the cylinder sleeve is made of stainless steel. Such a cylinder sleeve made of stainless steel is in particular wear- and corrosion-resistant, whereby a permanent use in an axial piston machine, which is driven by means of steam, is feasible without any problems. As an alternative to this, the cylinder sleeve can also be made of a steel alloy with the following components, 3.20-3.50% by weight of C, 1.60-2.10% by weight of Si, 0.60-0.80% by weight of Mn, 0.35-0.50% by weight of P, maximally 0.06% by weight of S, 0.20-0.40% by weight of Cr, 0.30-0.50% by weight of Mo and iron for the remainder.

In the case of a further advantageous embodiment of the solution according to the invention, the wobble-plate chamber is closed off by a second cover, which is designed as shaped sheet-metal part. Analogous to the first cover, which is designed as shaped sheet-metal part and which, together with the vapor-chamber housing part, defines the vapor chamber, the wobble-plate chamber can thus also be closed off by means of such a cover on the axially opposite side, which also contributes to designing the wobble-plate housing part more cost-efficiently and more easily here.

In the case of an advantageous further development of the solution according to the invention, the cup and ball bearing, via which the individual pistons of the axial piston machine are connected to the wobble plate, has a collar, which protrudes radially outwards. The cylinder sleeve, in turn, has a cut-out, which is open towards the front side and into which the cut-out of the cup and ball bearing, which protrudes radially outwards, can dip. Provision is moreover made on the cup and ball bearing itself for two sliding feet, which are arranged adjacent to the cut-out and which are supported on the guide bushing. An exact translational adjustment of the respective cup and ball bearing can be forced by means of such an embodiment, because said cup and ball bearing is guided via its cut-out, which protrudes radially outwards, in the cylinder sleeve-side cut-out. The guide can thereby be supplemented in that a guide bushing comprising a cut-out, which is only open between the cylinder housing part and the wobble-plate housing part, is arranged in the wobble-plate housing part, wherein the cut-out of the cup and ball bearing, which protrudes radially outwards, is also guided in this cut-out in terms of a lock against rotation. The cut-out of the cylinder sleeve and the cut-out of the guide bushing thus form the entire guide track for the cut-out of the cup and ball bearing, which protrudes radially outwards.

Advantageously, provision is made for at least one blind plug for one of the cylinders, which can be inserted into one of the cylinders instead of a cylinder sleeve and which closes the inlet opening thereof, which faces the vapor chamber. A power reduction of the axial piston machine according to the invention can hereby in particular be attained in a comparatively simple manner, because not all cylinders are used to generate power any longer, but only those, which are not closed by such a blind plug. By selecting the number of the used blind plugs, the respectively desired power of the axial piston machine can thus be influenced individually.

In the case of an advantageous further development of the solution according to the invention, the first cover has projections, which are embossed in the direction of the vapor chamber, which reduce the volume of the vapor chamber. The volume in the vapor chamber itself can be dimensioned exactly via these projections, which can also be used as reinforcement for the cover, whereby tests have shown that in particular a coordination, for example of the volume of the vapor chamber, of a displaced volume of a cylinder, as well as of a cross section of an inlet into the vapor chamber, has a significant influence on the efficiency of the axial piston machine. Particularly preferably, the volume of the vapor chamber is thereby between 30 cm³ and 100 cm³, while a cross section of an inlet into the vapor chamber is between 78 mm² and 200 mm². The displaced volume of the cylinder is between 25 cm³ and 75 cm³. This applies in particular for an axial piston machine comprising six cylinders. The three above-mentioned variables, thus the volume of the vapor chamber, the cross section of the inlet and the displacement volume of the cylinder, are thereby dependent on one another and thus do not only determine the efficiency, but also the response behavior of the axial piston machine significantly. In order to be able to obtain a response behavior, which is as quick as possible, the working chamber should have as little dead volume as possible. So that pressure fluctuations nonetheless do not result in the case of reduced steam volume in the working chamber, the inlet needs to be chosen to be correspondingly large. The quick provision of steam thereby also has a positive effect on a quick response behavior of the axial piston machine. The displaced volume of a cylinder thereby determines the required amount of steam per actuation. Moreover, the volume of the vapor chamber is also linked to the speed of the rotor, which determines the number of actuations per time. Optimal conditions both with regard to the response behavior and also with regard to the efficiency can be obtained thereby within the above-mentioned ranges of the volume of the vapor chamber, of the cross section of the inlet, and of the displaced volume of the cylinder.

In the case of a further advantageous embodiment of the solution according to the invention, the first cover has at least two connections for connecting in particular a pressure sensor or a temperature sensor, which are attached to a flat front surface of the first cover. A small sealing surface and a comparatively simple mounting can be obtained by arranging the connections on the flat surface of the first cover.

In the case of an advantageous embodiment of the solution according to the invention, partial ribs are arranged on the wobble-plate housing, wherein these ribs, for example together with the wobble-plate housing part, can be designed as integral cast part. The ribs themselves can thereby serve as reinforcement or also to enlarge the surface, whereby an improved cooling can be obtained. This cooling effect is in particular desired in the area of the wobble-plate housing, all the way to the discharge channels.

In the case of a further advantageous embodiment of the solution according to the invention, at least one of the housing parts has a corrosion-protection layer on an inner side. By means of such a corrosion-protection layer, in particular a corrosion process, triggered by the vapor used in the axial piston machine to drive the latter, can at least be reduced. In addition or in the alternative, provision can also be made for an insulating element, in particular a so-called insulating plate, which surrounds at least the vapor chamber, preferably also the cylinder chamber all the way to the outlets, by forming an air gap. By means of such an insulating element, an insulating layer of air can be created in particular around the vapor chamber, whereby the steam remains hot for a longer period of time in the vapor chamber itself, and a comparatively high efficiency can thus be obtained.

Further important features and advantages of the invention follow from the subclaims, from the drawings, and from the corresponding figure description by means of the drawings.

It goes without saying that the above-mentioned features and the features, which will still be discussed below, cannot only be used in the respectively specified combination, but also in other combinations or alone, without leaving the scope of the invention at hand.

Preferred exemplary embodiments of the invention are illustrated in the drawings and will be discussed in more detail in the description below, whereby the same reference numerals refer to the same or to similar or functionally identical components.

BRIEF DESCRIPTION OF THE DRAWINGS

In each case schematically,

FIG. 1 shows a sectional illustration through an axial piston machine according to the invention,

FIG. 2 shows a sectional illustration along the sectional plane A-A,

FIG. 3 shows a sectional illustration through the axial piston machine comprising passage openings arranged at different heights,

FIG. 4 shows a sectional illustration through the axial piston machine comprising an inclined valve disk opening,

FIG. 5 shows a sectional illustration through a horizontal axial piston machine comprising a lubrication line in a high-pressure area,

FIG. 6 shows a sectional illustration through a horizontal axial piston machine comprising a lubrication line in a low-pressure area.

DETAILED DESCRIPTION

According to FIGS. 1 and 3 to 6, an axial piston machine 1 according to the invention, which can for example be part of a heat recovery system 2 in a motor vehicle, which is not illustrated in detail, has a housing 3, in which a vapor chamber 4, a cylinder chamber 5 and a wobble-plate chamber 6 are provided. Cylinders 8, in which pistons 9 are arranged in a translationally movable manner, are provided annularly around a shaft 7 in the cylinder chamber 5. A valve disk 10, which is connected to the shaft 7 in a rotationally fixed manner, is arranged in turn in the vapor chamber 4, comprising a valve disk opening 11, which, in the illustration shown according to FIG. 1, is arranged so as to be aligned with an inlet opening 12 of the respective cylinder 8, depending on the angle of rotation. In this state, steam stored in the vapor chamber 4 can flow via the valve disk opening 11 and the inlet opening 12 into the corresponding cylinder 8 and can press down the piston 9 located therein. A wobble plate 14, which is connected to one of the pistons 9 via a cup and ball bearing 13 each and which is coupled to the shaft 7 in a rotationally fixed manner, is arranged in the wobble-plate chamber 6. Each cup and ball bearing 13 thereby has a sliding block, which has two sliding block halves. According to the invention, the housing 3 now has a vapor-chamber housing part 15, a cylinder housing part 16 and a wobble-plate housing part 17, which are connected to one another and, together, form the housing 3. Moreover, a cylinder sleeve 18 comprising a radially protruding collar 19 is provided in at least one of the cylinders 8, wherein the cylinder sleeve 18 is retained by means of its collar 19 in a cut-out 21 in the cylinder housing part 16, which adjoins a parting plane 20 between the vapor-chamber housing part 15 and the cylinder housing part 16. Moreover, the vapor chamber 4 is closed off by means of a first cover 24, which is connected to the vapor-chamber housing part 15, for example screwed together, and which is designed as a shaped sheet-metal part. This makes it possible to insert the cylinder sleeve 18 into the cylinder 8 from the vapor-chamber side and to subsequently attach the vapor-chamber housing part 15. By means of the multi-part design of the housing 3 according to the invention, it can be made in a simpler and more cost-efficient manner than for example a one-part or even integral housing used to date in this context.

The cylinder sleeve 18 can thereby be made of stainless steel and can thus not only have a comparatively high wear resistance, but also an insensitivity to corrosion, which is highly advantageous in particular for the axial piston machine 1, which is operated by means of steam. In addition or in the alternative, the cylinder sleeve 18 can also be provided with a coating, in particular a polymer coating or a DLC coating, which reduces the wear and/or the friction. Moreover, the cylinder sleeve 18 can be designed in such a way that an at least partial immersion of the wobble plate 14 is made possible. In particular a more compact design can be obtained through this.

When taking a closer look at the cylinder sleeve 18, it can be seen that the latter has at least two passage openings 22 and 22′ in the area of a lower dead center of the piston 9, via which steam can be discharged. The passage openings 22, 22′ thereby communicate with a respectively corresponding discharge channel 23, 23′, lead into the wobble-disk chamber 6 and are defined by the cylinder housing part 16 on the one side and the cylinder sleeve 18 on the other side. Moreover, the cylinder sleeve 18 preferably has at least a third passage opening 38, which serves as auxiliary outlet and vents the cylinder 8 in response to a movement of the piston 9 to the upper dead center (OT).

Downwards, the wobble-plate chamber 6 is closed off by a second cover 24′, which is designed as shaped sheet-metal part and which is illustrated in FIG. 2.

When taking a closer look at FIG. 1, it can be seen that the cup and ball bearing 13 has a cut-off 25, which protrudes radially outwards, the cylinder sleeve 18 has a cut-out 26, which is open towards the front side, that is, towards the bottom in the following example, into which the cut-out 25 can dip. Moreover, two sliding feet 27, 27′, which are arranged adjacent to the cut-out 25 and which are supported on the guide bushing 33, are arranged on the cup and ball bearing 13, as can be seen from FIG. 2. The cut-out 26 in the cylinder sleeve 18 is thereby preferably arranged in the area of the discharge channel 23 and can also be guided therein. In addition, the guide sleeve 18 can also be designed in such a way that the wobble plate 14 can dip in. The cut-outs 26, the passage openings as well as further areas of the cylinder sleeve 18 can be rounded in a hydro-erosive manner.

Moreover, provision can be made for at least one blind plug 28 for one of the cylinders 8, which can be inserted into the cylinder 8 instead of a cylinder sleeve 18 and which closes the inlet opening 12 facing the vapor chamber 4, as it is illustrated according to FIG. 1. The efficiency of the axial piston machine 1 can be regulated via the variation of the number of the blind plugs 28 in a comparatively simple manner.

When taking a closer look at the first cover 24, it can be seen that the latter is embodied so as to be substantially flat and has projections 29 embossed in the direction of the vapor chamber 4, which reduce the volume of the vapor chamber 4 and effect an additional reinforcement of the first cover 24. By providing corresponding projections 29, the volume of the vapor chamber 4 can also be determined exactly by means of a simple design of the first cover 24.

A volume of the vapor chamber 4 of between 30 cm³ and 100 cm³, a cross section of an inlet 30 of between 78 mm² and 200 mm² as well as a displaced volume of a cylinder 8 of between 25 cm³ and 75 cm³ has proven to be particularly advantageous. The three above-mentioned variables, that is, the volume of the vapor chamber 4, the cross section of the inlet 30 and the displacement volume of the cylinder 8, are thereby dependent on one another and thus determine the response behavior of the axial piston machine 1 as well as the efficiency thereof significantly. The working chamber should thereby have as little dead volume as possible, in order to improve the response behavior. So that pressure fluctuations nonetheless do not result in the case of reduced vapor volume in the working chamber, the inlet needs to be chosen correspondingly large. It goes without saying that the volume of the travel of the piston 9 then determines the required amount per actuation. In addition, this is then also linked to the speed, which determines the number of actuations per time. A large vapor chamber 4 would be ideal for a quick actuation, because sufficient steam is then always present and because pressure fluctuations do not result.

When taking a closer look at FIGS. 1 and 2, it can be seen that ribs 32 are arranged on the wobble-plate housing part 17, wherein the wobble-plate housing part 17 together with the ribs 32 could for example be designed as integral cast part. The ribs 32 thereby do not only reinforce the wobble-plate housing part 17, but also enlarge the surface thereof to the outside and thus effect an improved cooling. The integral embodiment of the ribs 32 with the wobble-plate housing part 17 allows for the cost-efficient production thereof.

Provision can moreover be made in the wobble-plate housing part 17 for a guide bushing 33 comprising a cut-out 26′, which is open only between the cylinder housing part 16 and the wobble-plate housing part 17 and into which the cut-out 25 dips. The guide bushing 33 can thereby also be made of stainless steel and can thus be designed to be wear-resistant as well as corrosion resistant. Particularly advantageously, it can also be provided with a friction and/or wear-reducing coating. In the mounted state, the cut-out 26′ of the guide bushing 33 is thereby aligned with the cut-out 26 of the cylinder bushing 18 and thus forms a guide track for the cut-out 25 of the cup and ball bearing 13, which protrudes radially outwards.

To be able to also reliably mount the guide bushing 33 in the housing 3 of the axial piston machine 1, said guide bushing has a radially protruding collar 19′, via which it is retained in a separating plane 20′ between the cylinder housing part 16 and the wobble-plate housing part 17. For mounting purposes, the guide bushing 33 is thereby inserted into the wobble-plate housing 17 from the top (based on FIG. 1), until it comes to rest in the separating plane 20′ with its collar 19′.

On an inner side, at least one of the housing parts 15, 16, 17 can additionally have a corrosion protection layer 34, by means of which the corrosion resistance can also be increased.

When taking a closer look at FIG. 1 once again, an insulating element 35, in particular an insulating plate, can be seen, which surrounds and thus insulates at least the vapor chamber 4 and, in the case at hand, additionally also the cylinder chamber 5 by forming an air gap 36. Cooling down the steam too quickly in the vapor chamber 4 connected with the loss of efficiency associated therewith can be prevented through this. The insulating element 35 can be fixed to the housing 3, in particular to the cover 24, for example by means of a screw connection. At least two connections 37 and 37′ for connecting a measuring sensor system, in particular for connecting a pressure sensor and/or a temperature sensor, which are in particular arranged in the area of a flat front surface of the first cover 24, can moreover be arranged on the first cover 24. A flat sealing surface, which can be sealed simply or easily, can be provided through this.

When looking at the axial piston machine 1 of FIG. 3, it can be seen that the passage openings 22, 22′ thereof are arranged at different heights. Discharge channels 23 comprising subsequent lubricating points 42 can preferably be opened by means of the different height arrangement of the outlet slots (passage openings) and can thus be provided with more exhaust steam with oil. In FIG. 3, the inner right passage opening 22′, for example, opens a little earlier, so that the exhaust steam with oil preferably flows inwards and for example the cup and ball bearing 13 as well as the wobble disk 14 can be lubricated.

FIG. 4 shows a sectional illustration through the axial piston machine 1 comprising an inclined valve disk opening 11, by means of which it can be obtained that oil flowing to the outside as a result of the centrifugal force (arrow) accumulates in the collecting area 44, can be directed onto the underside of the valve disk 10, and thus reaches the contact surfaces to the inlet valve seat. One or a plurality of holes can thereby be arranged in the valve disk 10. The valve disk opening 11 can also take over the function of cut-out 39, which can be seen on the left, for the mass balancing.

FIG. 5 shows a sectional illustration through a horizontal axial piston machine 1 comprising a lubrication line 40 in a high pressure area 41. Depending on the installation position of the axial piston machine 1, the lubrication line 40 needs to be installed in such a way that it leads from the collecting area 44, in which the oil drops collect, to the lubricating points 42, here a sealing sleeve 43. In the section, the lubrication line 40 is thereby drawn so as to lead through the inlet opening 12, which is to only serve to clarify the line routing. It goes without saying that, in reality, the lubrication line 40 does not cross the inlet opening 12. The pressure difference from the vapor chamber 4 to the surface above the sealing sleeve 41 is the driving force. Ideally, the lubrication line 40 can be designed as bead in the vapor-chamber housing part 15. The collection areas 44 for oil drops (by means of centrifugal force and or gravity) are thereby positioned in such a way that it can flow from there through the lubrication line 40 to locations 42 in the high-pressure area 41, which are to be lubricated and/or sealed.

Finally, FIG. 6 shows a sectional illustration through an axial piston machine 1, which is also horizontal, comprising a lubrication line 40 in a low-pressure area 45. The collection areas 44 for oil drops (by means of centrifugal force and or gravity) are thereby positioned in such a way that that it can flow from there through the lubrication line 40 to locations 42 in the low-pressure area 45, which are to be lubricated and/or sealed. Depending on the installation position of the axial piston machine 1, the lubrication line 40 needs to be installed in such a way that it leads from the collecting area 44, in which the oil drops collect, to the lubricating points 42 in the low-pressure area 45. The pressure difference from the vapor chamber 4 to the evaporation area is the driving force. A flow restrictor 46 can be installed in order to prevent steam from flowing through the lubrication line 40, when no oil is located therein.

A particularly simple and thus also cost-efficiently constructed axial piston machine 1 can be realized by means of the axial piston machine 1 according to the invention, which, due to the housing, which is designed in several parts, is also extremely flexible, in particular with regard to a possible adaptation. Moreover, it is a large advantage that, by means of the first cover 24, which is designed as cast part, the vapor-chamber housing part 15 can also be designed more easily and more cost-efficiently as compared to common housing parts installed therein. 

1. An axial piston machine, comprising: a housing having a vapor chamber, a cylinder chamber and a wobble-plate chamber; cylinders arranged annularly around a shaft in the cylinder chamber and having pistons arranged therein in a translationally movable manner; a valve disk connected to the shaft in a rotationally fixed manner and arranged in the vapor chamber; a wobble plate connected to one of the pistons via a cup and ball bearing and to the shaft in a rotationally fixed manner, the wobble plate being arranged in the wobble-plate chamber; wherein the housing has a steam-chamber housing part, a cylinder housing part, and a wobble-plate housing part connected to one another; wherein a cylinder sleeve having a radially protruding collar is provided in at least one cylinder, wherein the cylinder sleeve is retained by via the collar in a cut-out in the cylinder housing part, which adjoins a parting plane between the vapor-chamber housing part and the cylinder housing part; and wherein the vapor chamber is closed off by a first cover, which is connected to the vapor-chamber housing part and which is designed as a shaped sheet-metal part.
 2. The axial piston machine according to claim 1, wherein at least one of: the cylinder sleeve is made of one of stainless steel or a steel alloy with 3.20-3.50% by weight of C, 1.60-2.10% by weight of Si, 0.60-0. 80% by weight of Mn, 0.35-0.50% by weight of P, maximally 0.06% by weight of S, 0.20-0.40% by weight of Cr, 0.30-0.50% by weight of Mo, and iron for the remainder; and the cylinder sleeve is provided with a coating configured to reduce at least one of wear and friction.
 3. The axial piston machine according to claim 1, wherein the cylinder sleeve has at least two passage openings for discharging steam and that communicate with corresponding discharge channels in the cylinder housing part, wherein the discharge channels are defined by the cylinder housing part and the cylinder sleeve.
 4. The axial piston machine according to claim 3, wherein the cylinder sleeve has at least a third passage opening, which serves as auxiliary outlet and vents the cylinder in response to a movement of the piston to an upper dead center position.
 5. The axial piston machine according to claim 1, wherein the wobble-plate chamber is closed off by a second cover, which is designed as a shaped sheet-metal part.
 6. The axial piston machine according to claim 1, wherein: the cup and ball bearing has a cut-out protruding radially outwards; the cylinder sleeve has a cut-out, which is open towards a front side and in which the cut-out of the cup and ball bearing is guided in terms of a lock against rotation; and the cup and ball bearing has two sliding feet arranged adjacent to the cut-out of the cup and ball bearing and supported on a guide bushing.
 7. The axial piston machine according to claim 1, wherein at least one of: at least one blind plug is provided for one of the cylinders and is insertable into the one of the cylinders instead of a cylinder sleeve and closes an inlet opening of the one of the cylinders that faces the vapor chamber; and the cylinder sleeve is designed in such a way that it provides for an at least partial immersion of the wobble plate.
 8. The axial piston machine according to claim 1, wherein the first cover has projections embossed in a direction of the vapor chamber, the projections reducing a volume of the vapor chamber.
 9. The axial piston machine according to claim 1, wherein the first cover has at least two connections for connecting a pressure sensor or a temperature sensor to a flat front surface of the first cover.
 10. The axial piston machine according to claim 1, wherein at least one of: a volume of the vapor chamber is between 30 and 100 cm³; a cross sectional area of an inlet into the vapor chamber is between 78 mm² and 200 mm; and a displaced volume of the cylinder is between 25 cm³ and 75 cm³.
 11. The axial piston machine according to claim 1, further comprising ribs arranged in the wobble-plate housing part.
 12. The axial piston machine according to claim 11, wherein the wobble-plate housing part together with the ribs is designed as an integral cast part.
 13. The axial piston machine according to claim 6, wherein the guide bushing includes a cut-out, which is only open between the cylinder housing part and the wobble-plate housing part, is arranged in the wobble-plate housing part, and into which the cut-out of the cup and ball bearing dips.
 14. The axial piston machine according to claim 13, wherein the guide bushing is made of stainless steel.
 15. The axial piston machine according to claim 13, wherein the guide bushing has a radially protruding collar that retains the guide bushing in a separating plane between the cylinder housing part and the wobble-plate housing part.
 16. The axial piston machine according to claim 1, wherein at least one of the housing parts has a corrosion protection layer on an inner side.
 17. The axial piston machine according to claim 1, further comprising an insulating element, which surrounds at least the vapor chamber by forming an air gap.
 18. The axial piston machine according to claim 17, wherein the insulating element is screwed to the vapor-chamber housing part.
 19. A heat recovery system in a motor vehicle comprising an axial piston machine including: a housing having a vapor chamber, a cylinder chamber and a wobble-plate chamber; cylinders arranged annularly around a shaft in the cylinder chamber and having pistons arranged therein in a translationally movable manner; a valve disk connected to the shaft in a rotationally fixed manner and arranged in the vapor chamber; a wobble plate connected to one of the pistons via a cup and ball bearing and to the shaft in a rotationally fixed manner, the wobble plate being arranged in the wobble-plate chamber; wherein the housing has a steam-chamber housing part, a cylinder housing part, and a wobble-plate housing part connected to one another; wherein a cylinder sleeve having a radially protruding collar is provided in at least one cylinder, wherein the cylinder sleeve is retained via the collar in a cut-out in the cylinder housing part, which adjoins a parting plane between the vapor-chamber housing part and the cylinder housing part; and wherein the vapor chamber is closed off by a first cover, which is connected to the vapor-chamber housing part and which is designed as a shaped sheet-metal part.
 20. An axial piston machine comprising: a housing having a vapor chamber, a cylinder chamber and a wobble-plate chamber; cylinders arranged annularly around a shaft in the cylinder chamber and having pistons arranged therein in a translationally movable manner; a valve disk connected to the shaft in a rotationally fixed manner and arranged in the vapor chamber; a wobble plate connected to one of the pistons via a cup and ball bearing and to the shaft in a rotationally fixed manner, the wobble plate being arranged in the wobble-plate chamber; wherein the housing has a steam-chamber housing part, a cylinder housing part, and a wobble-plate housing part connected to one another; wherein a cylinder sleeve having a radially protruding collar is provided in at least one cylinder, wherein the cylinder sleeve is retained via the collar in a cut-out in the cylinder housing part, which adjoins a parting plane between the vapor-chamber housing part and the cylinder housing part; wherein the vapor chamber is closed off by a first cover, which is connected to the vapor-chamber housing part and which is designed as a shaped sheet-metal part; wherein the cup and ball bearing has a cut-out protruding radially outwards; wherein the cylinder sleeve has a cut-out, which is open towards a front side and in which the cut-out of the cup and ball bearing is guided in terms of a lock against rotation; and the cup and ball bearing has two sliding feet arranged adjacent to the cut-out of the cup and ball bearing and supported on a guide bushing. 